The world has two opposing sides: where there is light, there is darkness; where there is yin, there is yang. They are eternally opposed, yet forever connected. See how the protagonist, who transmigrates into Naruto, brings the two opposing sides together and creates chaos, the end and beginning of all things.
If he sees it through to the end, he'll eventually return to the Primordial World, I suppose. That's a little spoiler.
I wonder whether technology and cultivation count as opposing realms?
This story and its characters are entirely fictional. Any resemblance to actual people or events is purely coincidental. Do not imitate.
